2620075 icd for spg to archive ii user

Document Number 2620075 Code Identification 0WY55

WSR-88D ROC Build Date 2/4/2020

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INTERFACE CONTROL DOCUMENT FOR THE

SPG TO ARCHIVE II/USER PREPARED BY:

WSR-88D Radar Operations Center 1313 Halley Circle Norman, OK 73069

SUBMITTED & APPROVED FOR USE AS PRODUCT BASELINE BY: DATE:

Cheryl A. Stephenson Chief, Program Branch WSR-88D Radar Operations Center

DISTRIBUTION STATEMENT A: Approved for public release; distribution unlimited.



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INTERFACE CONTROL DOCUMENT

FOR THE SPG TO ARCHIVE II/USER 2620075

DOCUMENT REVISION RECORD FORM REVISION - RELEASED BY ROC RELEASE DATE 2/4/2020 EFFECTIVITY 2/4/2020 AUTHORITY ECP SPG-0057 FAST TRACK NO REV HISTORY SPG BLD 10.0 Section 1.0 - Section 2.0 - Section 3.0 - Section 4.0 - Appendix A - Appendix B - Appendix C -

REVISION RECORD Revision Description Date Initial Release Initial Release (SPG-SW-19-00078) 2/4/2020



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TABLE OF CONTENTS

1 SCOPE ............................................................................................................................................................ 1-1

1.1 Identification ........................................................................................................................................... 1-1

1.2 System Overview ..................................................................................................................................... 1-1

2 REFERENCE DOCUMENTS ....................................................................................................................... 2-1

2.1 Specifications: .......................................................................................................................................... 2-1

2.2 Other Publications: ................................................................................................................................. 2-1

2.3 Request For Comments (RFCs) .............................................................................................................. 2-2

3 ARCHIVE II TRANSPORT LAYER .............................................................................................................. 3-1

3.1 Applicable Standard ............................................................................................................................... 3-1

3.2 Transport Header Description ............................................................................................................... 3-1

4 ARCHIVE II APPLICATION LAYER .......................................................................................................... 4-1

4.1 Application Programming Interface (API) ............................................................................................ 4-1

4.1.1 LDM Overview ................................................................................................................................. 4-1

4.1.2 LDM Distribution ............................................................................................................................ 4-1

4.1.3 LDM Support ................................................................................................................................... 4-1

4.1.4 LDM Platforms ................................................................................................................................ 4-1

4.2 Connection Procedure ............................................................................................................................. 4-1

4.3 Data Exchange ........................................................................................................................................ 4-1

4.3.1 LDM Database Keys ........................................................................................................................ 4-2

4.3.2 Archive II Data Stream ................................................................................................................... 4-2

4.3.3 Volume Header Record .................................................................................................................... 4-2

4.3.4 LDM Compressed Record ................................................................................................................ 4-2

4.3.5 Metadata Record .............................................................................................................................. 4-3

4.3.6 LDM Data Processing ...................................................................................................................... 4-3

4.3.6.1 LDM Data Processing Example ............................................................................................... 4-3

4.3.6.1.1 LDM Raw Data File Format ................................................................................................ 4-3

4.3.6.2 NCEI Data Format ................................................................................................................... 4-4

4.4 Disconnection .......................................................................................................................................... 4-4

4.5 Archive II Data ........................................................................................................................................ 4-4

4.5.1 Functional Description .................................................................................................................... 4-4

4.6 Archive II Message Types ....................................................................................................................... 4-5

4.6.1 Message Type-2 RDA Status Data ................................................................................................. 4-5

4.6.2 Message Type-5 RDA Volume Coverage Pattern Data ................................................................. 4-5

4.6.3 Message Type-29 Model Data Message .......................................................................................... 4-5

4.6.4 Message Type-31 Digital Radar Data Generic Format ................................................................. 4-5



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4.7 Message Sequence ................................................................................................................................... 4-5

Appendix A Acronymns/Abbreviations ........................................................................................................... A-1

Appendix B LDM Key Format ........................................................................................................................ B-1

Appendix C MESSAGE FIELDS DEFINED FOR SPG LEVEL II DATA ................................................... C-1

LIST OF FIGURES

Figure 1. Start of Volume Header Record Format ............................................................................................. 4-2 Figure 2. Raw File Format ................................................................................................................................... 4-4 Figure 3. Message Type Sequence ....................................................................................................................... 4-6

LIST OF TABLES

Table C-1: TDWR/SPG Alarm Messages: ........................................................................................................... C-4



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1 SCOPE

1.1 Identification

This document defines Terminal Doppler Weather Radar (TDWR) Archive II Interface. This document identifies applicable standards and defines the protocol, syntax, and meaning of the binary data transmission frames. This ICD is not intended to serve as a tutorial document concerning the applicable standards. That is, the reader is assumed to be generally knowledgeable of the contents, terminology, etc., of the standards. This document maps the unique aspects of new Archive II communications into the appropriate standard. Distribution of this document is unrestricted.

1.2 System Overview The TDWR acquires, generates, and distributes Doppler radar products for meteorological and hydrological applications. Specifically, the TDWR functional area acquires radar data; controls antenna, transmitter, and receiver electronics; prepares radar data in a digital format; transmits radar data and status to the Supplemental Product Generator (SPG). The SPG functional area receives radar data and status information from the TDWR, generates radar products, and distributes radar products for graphical and alphanumeric display systems such as the Advanced Weather Information Processing System (AWIPS). AWIPS also sends data to the SPG in the form of Model Data to be used in radar product generation. The Archive II functionality provides TDWR radar data to the National Level-II Network via the Unidata Local Data Manager (LDM) software. The data is then distributed to various level-II top tiers and ultimately the level-II user community.



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2 REFERENCE DOCUMENTS The following documents are referenced herein. In the event of a conflict between the documents referenced herein and the contents of this document, the contents of this document shall be considered a superseding requirement.

2.1 Specifications:

2810003

SPG System Specification For NWS use of TDWR

2620063 Interface Control Document for SPG to Class 1 User

Source: WSR-88D Radar Operations Center 1313 Halley Circle Norman, OK 73069 URL: http://www.roc.noaa.gov

2.2 Other Publications:

Unidata LDM Documentation

Local Data Manager (LDM) Documentation and Software

Source: UCAR Office of Programs Unidata Program Center P.O. Box 3000 Boulder, CO 80307-3000 URLs: http://www.unidata.ucar.edu http://my.unidata.ucar.edu/content/software/ldm

Michael Burrows and D. J. Wheeler: 5/10/94. Digital SRC Research Report 124.

A block-sorting lossless data compression algorithm. (This is the basis for bzip2). ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz

libbzip2 version 1.0.2. bzip2 library by Julian Seward

bzip2 and libbzip2

The bzip2 and libbzip2 official home page.

Source: The bzip2 utility used in this ICD is a component of the RedHat Enterprise Linux Operating System. The source can be found at: URL: http://www.bzip.org

MIL-STD-1777 Internet Protocol

MIL-STD-1778 Transmission Control Protocol

Source: Documentation Automation and Production Service Building 4/D 700 Robins Avenue Philadelphia, PA 19111-5094



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2.3 Request For Comments (RFCs)

Reference Number Title RFC 793 Transmission Control Protocol

RFC 4506 External Data Representation Source: Internet Architecture Board (IAB)

Internet Engineering Task Force (IETF) URL: http://www.ietf.org/home.html



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3 ARCHIVE II TRANSPORT LAYER

3.1 Applicable Standard

The transport layer for this interface will support the Transmission Control Protocol (TCP) as specified in RFC 793 and MIL-STD 1778 and as clarified in RFC 1122.

3.2 Transport Header Description

Connection-oriented transport service is implemented using TCP. TCP is a connection-oriented, end-to-end reliable protocol designed to fit into a layered hierarchy of protocols which support multi-network applications. It provides for guaranteed delivery of data between pairs of processors in host computers attached to networks outside the TDWR/SPG system. The TCP port number used will be the well-known LDM TCP port 388.



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4 ARCHIVE II APPLICATION LAYER The OSI Model Session, Presentation, and Application layers are defined by an Applications Programming Interface (API), and the format of the messages which are transferred.

4.1 Application Programming Interface (API) The interface between TCP and an application process consists of a set of calls much like the calls an operating system provides to an application process for manipulating files. There are calls to open, put, get, or close the LDM data store queues. The Archive II application uses the LDM API to manage the data and the TCP/IP transmission protocols.

4.1.1 LDM Overview Unidata's Local Data Manager (LDM) software acquires data and shares them with other networked computers. A data product is treated as an opaque unit, thus nearly any data can be relayed. Data can either be ingested directly from a data source by a client ingestor, or the LDM server can talk to other LDM servers to either receive or send data. Ingestors scan the data stream, determine product boundaries, and extract products, passing those products on to the server product queue. The data, in turn, can be processed locally and/or passed on to other LDM servers. The LDM server software used by Archive II is configured to store products and allow them to be forwarded to other LDM servers.

4.1.2 LDM Distribution

The Unidata Program Center distributes the LDM software via FTP and WWW at http://www.unidata.ucar.edu/packages/ldm/. Note: LDM data should not be shared outside the receiving organization without the approval of the data provider.

4.1.3 LDM Support For further information contact: UCAR Unidata Program Center P.O. Box 3000 Boulder, Colorado, USA 80307 (303) 497-8643 Internet: [email protected]

4.1.4 LDM Platforms

The LDM is designed to run on a UNIX/Linux workstation. The following items comprise the minimum platform requirements: UNIX/Linux workstation, adequate disk storage for data, TCP/IP Ethernet, standard C compiler (unless the LDM binary version is downloaded), and Perl. The workstation must also maintain a monotonic clock accurate to within one second.

4.2 Connection Procedure Based upon entries in its ldmd.conf file, the user's LDM server initiates data exchange with another LDM server by establishing a network connection and requesting data. If the other LDM’s ldmd.conf file contains an entry to allow the request, the connection is made and data transferred.

4.3 Data Exchange This section describes the end-user data structures and values used to store and retrieve Archive II data with the LDM. It also covers the data structures unique to the Archive II data in the LDM context.



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4.3.1 LDM Database Keys Each LDM data record is assigned a key and feedtype when it is placed into the LDM queue. This key is used to assemble and gather like data records. The key is crucial to correctly assemble the records that comprise a complete volume of TDWR Level II data. The LDM feedtype for Archive II is NEXRD2. See Appendix B - LDM Key Format for a detailed description of the format.

4.3.2 Archive II Data Stream Within the LDM storage context, at the beginning of the Archive II data stream is an Archive II Volume Header Record. The Volume Header Record is fixed length and contains information uniquely identifying the format and the data that follows. Following the Volume Header Record are variable-length records containing the Archive II data messages. These records are referred to as LDM Compressed Record(s).

4.3.3 Volume Header Record

At the start of every volume is a 24-byte record describing certain attributes of the radar data. The first 9 bytes is a character constant of which the last 2 characters identify the version. The next 3 bytes is a numeric string field starting with the value 001 and increasing by one for each volume of radar data in the queue to a maximum value of 999. Once the maximum value is reached the value will be rolled over. The combined 12 bytes are called the Archive II filename. The next 4 bytes contain the SPG-modified Julian date of the start of volume radial followed by 4 bytes containing the time of the start volume radial. The date and time integer values are big Endian format. The last 4 bytes contain a 4-letter radar identifier assigned by ICAO. See Figure 1 for header format. 9 bytes 3 bytes 4 bytes 4 bytes 4 bytes Tape Filename:‘AR2V00xx.’*

Extension Number: '001'

Date**: SPG-modified Julian

Time***: Milliseconds past midnight

ICAO of radar

* xx indicates version where: Version 08: TDWR/SPG Level II data **Days since 1/1/1970 where 1/1/1970 equals day 1 ***The Archive II data timestamp comes from the TDWR radar data.

Figure 1. Start of Volume Header Record Format

4.3.4 LDM Compressed Record The structure of the LDM Compressed Record is a 4-byte, big-endian, signed binary control word followed by a compressed block of Archive II data messages. The control word contains the size, in bytes, of the compressed block not including the control word itself. As the control word contains a negative size under some circumstances, the absolute value of the control word must be used for determining the size of the block. The first compressed record is the Metadata Record, consisting of 134 messages (see section 7.3.5 Metadata Record for detailed information). Following the Metadata Record is a variable number of compressed records containing 120 radial messages (type 31) plus 0 or more TDWR/SPG Status messages (type 2). The method of compression used to build the compressed block is the bzip2 implementation of the Burrows-Wheeler block sorting text compression algorithm and Huffman coding. Following the variable number of radial message records is an optional Model Data compressed record. This record consists of the Model Data message (type 29). The Model Data message consists of the standard RDA/SPG message header (See Appendix C) following by model data. The message size defined in the



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message header is expressed using an alternate method for specifying size for messages larger than 65534 halfwords (see Appendix C). The format of the model data is described in the Interface Control Document for SPG to Class 1 User, 2620063.

4.3.5 Metadata Record The first LDM Compressed Record contains the Archive II messages comprising the Archive II metadata. The size of the uncompressed metadata is fixed at 134 messages, or 325888 bytes. The following table contains the message types in the sequence in which they are placed in the LDM Compressed Record. It contains the number of 2432 byte message segments set aside for each message type when they are uncompressed. In those instances where the message requires fewer segments than indicated the message type field of the excess message segments will be set to zero. For the TDWR/SPG metadata record, space is reserved for potential future additions and consists of 132 2432 byte segments. Each segment has the message type field set to zero. Message Type Number of Segments Reserved 132 5 1 2 1

4.3.6 LDM Data Processing The end user of Archive II data can use the LDM software to collect and manage the data. Data passed to the LDM server are processed in a variety of ways; how specific data are processed is determined by data identifiers and a configuration file called pqact.conf. Processing actions include placing the data in files and running arbitrary programs on the data. Decoders are also available from Unidata that interface with the LDM and convert data into the forms required by various applications.

4.3.6.1 LDM Data Processing Example The end user can take advantage of the LDM pqact which uses pattern matching to specify what actions are performed on each product after it is received or placed into the LDM queue. Pqact uses a configuration file called pqact.conf to set up the table of patterns and associated actions for products. This file is human-readable and editable. It contains a list of pattern-action entries, where a pattern is a (feed type, regular expression) pair. For example, the following entry could be placed into the pqact.conf file: NEXRD2<TAB>^L2-([^/]*)/(....)/([0-9][0-9][0-9][0-9][0-1][0-9][0-3][0-9][0-2][0-9][0-5][0-9][0-9][0-9]) /(.*)/(.*)/(.)/(V0[8])/(.) <TAB>FILE<TAB>/home/ldm/data/\2/\3.raw Note that the character string "<TAB>" is not part of the entry, rather it is used in this example to show where a horizontal tab character is required. This regular expression in the pqact.conf file is based upon the database key, and will cause all the volume data to be placed into a directory corresponding to the radar identifier (Key Field 2). Each volume of data will be in a file named after the date and time (Key Field 3) of that volume number (i.e. 20191016094746.raw). Key Field 6 is a single character denoting Start of Volume (S), Intermediate Data (I), End of Volume (E) or (M) Model Data. Key Field 7 is version number of the form Vxx where x takes on the values defined in Figure 1. Key Field 8 is a spare for future use. For more information refer to the LDM documentation. The format of this raw file is described Figure 2.

4.3.6.1.1 LDM Raw Data File Format To exploit the Archive II data the end user must develop a program to extract and decompress the data stored in the LDM raw data file. The libbz2 library function BZ2_bzBuffToBuffDecompress can be used to decompress the LDM Compressed Record. Once decompressed each message requires 2432 bytes of storage



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with the exception of Message Type 31 (Digital Radar Data Generic Format) and Message type 29 which are variable length. Message 29 is also formatted using External Data Representation (XDR).

Volume Header Record A 24-byte record that is described in Figure 1. This record will contain the volume number along with a date and time field.

LDM Compressed Record A record that is bzip2 compressed. It consists of Metadata message types 5, 2 and reserved types (type 0). See section 7.3.5.

LDM Compressed Record A variable size record that is bzip2 compressed. It consists of 120 radial data messages (type 1 or 31) plus 0 or more RDA Status messages (type 2). The last message will have a radial status signaling “end of elevation” or “end of volume”. See paragraph 7.3.4.

Repeat (LDM Compressed Record) Or

End of File (for end of volume data) Optional LDM Compressed Record A record that is bzip2 compressed consisting of the Model Data message. See paragraph 7.3.4.

Figure 2. Raw File Format

4.3.6.2 NCEI Data Format This document does not describe any other stored TDWR/SPG data formats once the data leaves the SPG. The data provided to the public by NCEI may be stored in a different format. For NCEI formats, refer to NCEI documentation.

4.4 Disconnection The SPG user can stop and start putting Archive II data into the LDM queue. It does not disconnect the LDM transfer stream. The downstream LDM server will remain connected waiting for new Archive II data to ingest.

4.5 Archive II Data

4.5.1 Functional Description Four (4) message types are archived. Three (3) message types are TDWR/SPG and one (1) is SPG:

* Message Type 31

Digital Radar Data Generic Format

Message types 2 and 5 constitute the Archive II metadata. The metadata describes the operational environment of the TDWR/SPG at the time the Archive II Digital Radar data was recorded.

* Message Type 2 TDWR/SPG Status Data * Message Type 5 TDWR Volume Coverage Data * Message Type 29 Model Data Message



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4.6 Archive II Message Types The messages following the Archive II filename are formatted according to the Appendix C except message type 29 which is formatted according to the SPG to Class 1 ICD. Each message is comprised of a message header followed by a data segment. The type of data contained within the message is identified by the message type field within the message header. The contents of the message header along with the eight (8) message types contained in the Archive II file are briefly described in this ICD. The Archive II raw data format contains a 28-byte header. The first 12 bytes are empty, which means the "Message Size" does not begin until byte 13 (halfword 7 or full word 4). This 12 byte offset is due to legacy compliance (previously known as the "CTM header"). See Appendix C for more details (Message Header Data).

4.6.1 Message Type-2 RDA Status Data Message type 2, TDWR/SPG Status Data, contains the state of operational functions within the TDWR/SPG and is written out to the Archive II interface each time the status of the TDWR/SPG changes. There will be at least one TDWR/SPG Status Data message written to the Archive II interface per Archive II volume. See Appendix C for details.

4.6.2 Message Type-5 RDA Volume Coverage Pattern Data Message type 5, TDWR Volume Coverage Pattern, is written to the Archive II interface once per Archive II volume. See Appendix C for details.

4.6.3 Message Type-29 Model Data Message The Message Type 29, Model Data Message, is written to the Archive II interface after the Archive II volume whenever Model Data is sent to the SPG from AWIPS. Model Data is received at the SPG approximately once every hour near the top of the hour.

4.6.4 Message Type-31 Digital Radar Data Generic Format Message type 31, Digital Radar Data Generic Format, contains one (1) radial of data. See Appendix C for details.

4.7 Message Sequence Following the Volume Header Record is the TDWR/SPG metadata for that volume. TDWR/SPG metadata (Message Types 2, and 5) consists of all pertinent TDWR/SPG data that was in effect when the volume of TDWR/SPG Digital Radar Data was recorded (Message Type 31). This pool of metadata is compressed and written to the LDM queue at the start of every volume. After the metadata is written out, message types 2 and 31 will be gathered and written to the LDM queue as described in the earlier sections. Following the end of the volume, an optional message type 29 is written to the LDM queue.

The Reserved segments and message types 2 and 5 are written to the Archive II queue in the following sequence (see Figure 3): Reserved Segments

Message Type 5 – Volume Coverage Pattern Data

Message Type 2 – RDA Status Data



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Figure 3. Message Type Sequence

TDWR/SPG Status Data, Message Type 2, is written to the Archive II interface as the status of the TDWR/SPG changes. There will be at least one Message Type 2 written to the Archive II interface per Archive II volume containing a complete TDWR/SPG Volume Scan. The structure of the data associated with Message Types 2, 5, and 31 are defined in Appendix C. The structure of the data associated with Message Type 29 is defined in Appendix C (for the message header) and the SPG to Class 1 User for the model data.



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APPENDIX A ACRONYMNS/ABBREVIATIONS

Acronym/ Abbreviation

Description

ANSI American National Standards Institute AWIPS Advanced Weather Information Processing System bzip2 Data Compression algorithm used CSMA/CD Carrier Sense Multiple Access with Collision Detection FW Full Word, four octets addressed by the location of either the high-order or

low-order octet. Usually an address that is 0 modulo 4. I/O Input/Output IAB Internet Architecture Board ICAO International Civil Aviation Organization ICD Interface Control Document ID Identification IP Internet Protocol ISO International Standards Organization LAN Local Area Network LDM Unidata Local Data Manager LSB Least Significant Bit MAC Media Access Control Mbps Million Bits per Second MSB Most Significant Bit NCEI National Centers for Environmental Information NEXRAD Next Generation Weather Radar NEXRD2 LDM Feedtype for Archive II data OS Operating System OSI Open Systems Interconnection RDA TDWR Radar Data Acquisition RFC Request for Change (IAB) RH NWS Regional Headquarters; Eastern, Southern, Central, and Pacific. SPG Supplemental Product Generator SCN Specification Change Notice TCP/IP Transmission Control Protocol/Internet Protocol TDWR Terminal Doppler Weather Radar VCP Volume Coverage Pattern WFO Weather Forecast Office XDR External Data Representation



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APPENDIX B LDM KEY FORMAT

L2-{CMPR_TYPE}/{ICAO}/{DATE_TIME}/{VOL}/{REC}/{S/E/I/M}/{Vxx}/0

CMPR_TYPE –Data Compression type in ASCII. At the time of publication only “BZIP2” is used. ICAO – Radar identifier in ASCII. The three uppercase character International Civil Aviation Organization identifier of the radar producing the data preceded by a (capital) “T”. DATE_TIME – The date and time in yyyymmddHHMMSS format. Where yyyy is year, mm is month, dd is day, HH is hour, MM is minute, and SS is second. This date and time comes from the radar time in Figure 2. VOL – The Volume ID 1-999. This will be the same number as the extension number found in the Volume Header Record. REC – The current record number in the volume. A record is a group of Archive II messages grouped and compressed together. The record number starts at 1. S/E/I/M – Record status. S indicates the first record of a volume, E indicates the last record of a volume, I indicates an intermediate record and M indicates a Model Data record. Vxx – The version number where xx is a 2 digit integer. See text under Figure 1 for a list of version numbers and their meanings. SPARE – Last field is hard coded as “0” and reserved for future use.

Example 1: L2-BZIP2/TOKC/20191016155526/154/4/I/V08/0 This example shows a key for a BZIP2 compressed record number 4 of volume 154 from the TOKC radar on 10/16/2019 at 15:55:26. The data is Message 31 TDWR/SPG. Example 2: L2-BZIP/TOKC/20191016155526/154/43/E/V08/0 This example shows a key for a BZIP2 compressed record number 43 of volume 154 from the TOKC radar on 10/16/2019 at 15:55:26 with an “E”nd of volume marker. The next record may be a Model Data record, otherwise the next record should start volume 155. The data is Message 31 TDWR/SPG.



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APPENDIX C MESSAGE FIELDS DEFINED FOR SPG LEVEL II DATA All message types include a 16 byte RDA/SPG message header that identifies the type, size and date/time of the message:

RDA/SPG Message Header Data NAME DESCRIPTION (3) FORMAT UNITS

(4) RANGE ACCURACY/

PRECISION BYTE LOCATION

Message Size

Message size in halfwords (1)

Integer*2 halfword 9 to 65535 1 0 and 1

RDA Redundant Channel

Channel Numbers for: 8 = Single Channel (bit 3 set) 9 = Redundant Channel 1 (bits 3 & 0 set) 10 = Redundant Channel 2 (bits 3 & 1 set)

Integer*1 N/A 0 to 10 1 2

Message Type

Integer code from Table I Integer*1 N/A 2, 5, 29, or 31

N/A 3

I.D. Sequence Number

Message Sequence Number Integer*2 N/A 0 to 65535 then roll over to 0

1 4 and 5

Julian Date Julian Date - 2440586.5 (2) Integer*2 d 1 to 65,535

1 6 and 7

Milliseconds of Day

Number of milliseconds from Midnight, Greenwich Mean Time

Integer*4 msec 0 to 86,399,999

± 2000/ ± 1

8 to 11

Number of Message Segments

Message larger than 1208 halfwords are segmented and transmitted separately except for Message 31 that has a segment size of 65535 halfwords (5)

Integer*2 N/A 1 to 65535 1 12 and 13

Message Segment Number

Segment number of this message

Integer*2 N/A 1 to 65535 1 14 and 15

Notes: 1. This is the message size for this message segment, not for the total of all segments in the message. 2. 1 January 1970 00.00 Greenwich Mean Time = 1 Modified Julian Date. 3. All bit locations are referenced to location 0 (LSB). 4. See Appendix A for unit definitions and standard symbology. 5. For all Data Message Types, the maximum segment size is 1208 halfwords except for Message Type 31, Digital Radar Data Generic Format, which can have a segment as large as 65535 halfwords. Following the Message Header, are message data applicable to the message type. The message format for RDA Status (Message Type 2), RDA VCP Data (Message Type 5) and Radial Message (Message Type 31) are defined below. For SPG Level II data, not all message fields are available or applicable, whereas others are set to fixed values that will not change. This Appendix describes possible values for various messages. Unless otherwise noted, fields that are not applicable or not available will be set to the value zero (0). (Note:



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Not Applicable refers to those items in which the information is not pertinent, e.g., Dual Pol specific values. Not Available refers to those items which are applicable but the specific value is unknown, e.g., calibration constant). TDWR Status (Message Type 2):

NAME DESCRIPTION FORMAT (1), (2)

UNITS (5)

RANGE (OR VALUE)

ACCURACY/ PRECISION

HALFWORD LOCATION

RDA STATUS Start-Up Operate Offline-Operate

Code*2 (4) N/A As Listed 2 (bit 1 set) 16 (bit 4 set) 64 (bit 6 set)

N/A 1

OPERABILITY STATUS

RDA - On-line RDA - Inoperable

Code*2 N/A As Listed 2 (bit 1 set) 32 (bit 5 set)

N/A 2

CONTROL STATUS

Local Only

Code*2 N/A As Listed 2 (bit 1 set)

N/A 3

AUXILIARY POWER GENERATOR STATE

Not Applicable

Integer*2 N/A 0

N/A 4

AVERAGE TRANSMITTER POWER

Peak Power from radial message

Integer*2 W 0-9999 +/- 1 +/- 1

5

HORIZONTAL REFLECTIVITY CALIBRATION CORRECTION (delta dBZ0)

Not Available Integer*2 N/A 0 N/A 6

DATA TRANSMISSION ENABLED

(All Data Enabled) Reflectivity Velocity Width

Code*2 N/A 4 (bit 2 set) 8 (bit 3 set) 16 (bit 4 set)

N/A 7

VOLUME COVERAGE PATTERN NUMBER

TDWR Pattern Selected

Integer*2 N/A -80 or -90 1 8

RDA CONTROL AUTHORIZATION

Not Applicable Integer*2 N/A 0 N/A 9

RDA BUILD NUMBER

RDA major & minor build version information

Scaled Integer*2

N/A 200(3) N/A 10

OPERATIONAL MODE

Operational

Code*2 N/A As Listed 4 (bit 2 set)

N/A 11

SUPER RESOLUTION STATUS

Not Applicable Integer*2

N/A 0 N/A 12



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UNITS (5)

RANGE (OR VALUE)

ACCURACY/ PRECISION

HALFWORD LOCATION

CLUTTER MITIGATION DECISION STATUS

Not Applicable

Integer*2 N/A 0 N/A 13

AVSET STATUS Not Applicable

Integer*2 N/A 0

N/A 14

RDA ALARM SUMMARY

No Alarms Receiver Communication

Code*2 N/A As Listed 0 (no bits set) 16 (bit 4 set) 64 (bit 6 set)

N/A 15

COMMAND ACKNOWLEDGMENT

Not Applicable

Integer*2 N/A 0 N/A 16

CHANNEL CONTROL STATUS


SPOT BLANKING STATUS

Status of Spot Blanking: Not Installed Enabled

Code*2 (4) N/A As Listed 0 (no bits set) 2 (bit 1 set)

N/A 18

BYPASS MAP GENERATION DATE


BYPASS MAP GENERATION TIME


CLUTTER FILTER MAP GENERATION DATE


CLUTTER FILTER MAP GENERATION TIME


VERTICAL REFLECTIVITY CALIBRATION CORRECTION


TRANSITION POWER SOURCE STATUS

Not Applicable Integer*2 NA 0 N/A 24

RMS CONTROL STATUS


PERFORMANCE CHECK STATUS

Not Applicable Integer*2 N/A 0

N/A 26



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UNITS (5)

RANGE (OR VALUE)

ACCURACY/ PRECISION

HALFWORD LOCATION

ALARM CODES One condition per halfword (Maximum of 14 alarms sent at a time). See Alarm Message Table C-1 for individual alarm codes. MSB set indicates alarm has been cleared.(6)

Integer*2 N/A 0 to 800 N/A 27 to 40

(1) All bit references start from 0 (LSB). (2) Unless otherwise indicated as mutually exclusive, Integer Code Formats can set multiple bits in the same message. For example, in case bits 1 and 2 are set, then the integer value passed would be 2 + 4 = 6. (3) If value divided by 100 is greater than 2, then the Build Version is the value divided by 100. Otherwise, the Build Version is value divided by 10. (4) Values listed are mutually exclusive. (5) See Appendix B for unit definitions and standard symbology. (6) For alarms, the following states are defined: IN = Inoperative, SEC = Secondary (secondary alarms are not specifically tied to a "STATE" change), and N/A = Not applicable. For alarm type, ED are alarms identified as ED (Edge Detected) and are reported every time the test associated with the alarm fails consecutively for a number of times equal to the alarm reporting count (see "Sample" column). Such alarms will be cleared (MSB set) when the test outcome first passes after the alarm is reported. The "DEVICE" column indicates the hardware device area where the alarm has occurred (if applicable); acronyms under the DEVICE column are as follows: RCV = Receiver, COM = TDWR RDA Communications. The “SAMPLE” column indicates the number of samples (failures) that must occur before this alarm is displayed. The "ALARM MESSAGE" column is an abbreviated description of the alarm message that is displayed at both the SPG.

Table C-1: TDWR/SPG Alarm Messages:

CODE STATE ALARM TYPE

DEVICE SAMPLE ALARM MESSAGE

0 N/A N/A N/A N/A NO ALARMS 1 IN ED COM 1 WIDEBAND FAILURE 2 IN ED COM 1 WIDEBAND DISCONTINUITY 3 SEC ED RCV 1 NO MOMENT DATA RADIAL COUNT EXCEEDED 4 SEC ED RCV 1 RADIAL DATA LOST



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TDWR Volume Coverage Pattern Data (Message Type 5)

NAME DESCRIPTION FORMAT(4) UNITS(10) RANGE (OR VALUE)(7)

ACCURACY/ PRECISION

HALFWORD LOCATION

MESSAGE SIZE Number of Halfwords in Message

Integer*2 halfword 23 to 755 1 1

PATTERN TYPE Constant Elevation Cut (11)

Code*2 N/A As listed 2

N/A 2

PATTERN NUMBER

Pattern Number Values

Integer*2 N/A 80 or 90 1 3

NUMBER OF ELEVATION CUTS

Number of elevation cuts in one complete volume scan

Integer*2 N/A 16 (VCP 90) 23 (VCP 80)

1 4

VERSION VCP version number

Integer*1 N/A 1 1 5 (1)

CLUTTER MAP GROUP NUMBER(12)

Not Applicable Integer*1 N/A 1 1 5 (2)

DOPPLER VELOCITY RESOLUTION

Doppler Velocity Resolution Values: 0.5 1.0

Code*1 m/s As Listed 2 (set bit 9) 4 (set bit 10)

N/A 6 (1)

PULSE WIDTH Pulse Width Values: Short

Code*1 N/A As listed 2 (set bit 1)

N/A 6 (2)

RESERVED N/A N/A N/A N/A N/A 7-8 VCP SEQUENCING Not Applicable Integer*2 N/A 0 N/A 9 VCP SUPPLEMENTAL DATA

Not Applicable Integer*2 N/A 0 10

RESERVED N/A N/A N/A N/A N/A 11 Repeat for each elevation angle (13)

ELEVATION ANGLE (3)

The elevation angle for this cut

Code*2 (6) deg 0.000000 to 359.956055

0.043945 E1

CHANNEL CONFIGURATION

Channel Configuration Values: Constant Phase

Code*1 N/A As Listed 0

N/A E2 (1)



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ACCURACY/ PRECISION

HALFWORD LOCATION

WAVEFORM TYPE Waveform Type Values: Contiguous Surveillance Contiguous Doppler w/o Ambiguity Resolution

Code*1 N/A As Listed (8)

1 4

N/A E2 (2)

SUPER RESOLUTION CONTROL

Not Applicable Integer*1 N/A 0 N/A E3 (1)

SURVEILLANCE PRF NUMBER(5)(14)

The pulse repetition frequency number for surveillance cuts

Integer*1 N/A 0 to 8 1 E3 (2)

SURVEILLANCE PRF PULSE COUNT/RADIAL(5)(1

4)

The pulse count per radial for surveillance cuts

Integer*2 N/A 0 to 999 1 E4

AZIMUTH RATE The azimuth rate of the cut

Code*2 (9) deg/s -30.0 to +30.0 0.1/0.1 E5

REFLECTIVITY THRESHOLD (14)

Signal to noise ratio (SNR) threshold for reflectivity

Scaled SInteger*2

dB -12.0 to +20.0 .125 E6

VELOCITY THRESHOLD (14)

Signal to noise ratio (SNR) threshold for velocity

Scaled SInteger*2

dB -12.0 to +20.0 .125 E7

SPECTRUM WIDTH THRESHOLD (14)

Signal to noise ratio (SNR) threshold for spectrum width

Scaled SInteger*2

dB -12.0 to +20.0 .125 E8

DIFFERENTIAL REFLECTIVITY THRESHOLD

Not Applicable Integer*2 N/A 0 N/A E9

DIFFERENTIAL PHASE THRESHOLD


CORRELATION COEFFICIENT THRESHOLD




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ACCURACY/ PRECISION

HALFWORD LOCATION

EDGE ANGLE (14) Sector 1 Azimuth Clockwise Edge Angle (denotes start angle)

Code*2 (6) deg 0.000000 to 359.956055

0.043945 E12

DOPPLER PRF NUMBER(5)(14)

Sector 1 Doppler PRF Number


DOPPLER PRF PULSE COUNT/RADIAL(5)(1

4)

Sector 1 Doppler Pulse Count/Radial


SUPPLEMENTAL DATA


SAME AS E12 to E14 FOR SECTOR 2

E16 to E18

EBC ANGLE Not Applicable Integer*2 N/A 0 N/A E19 SAME AS E12 to E14 FOR SECTOR 3

E20 to E22

RESERVED N/A N/A N/A N/A N/A E23 (1) Upper byte. (2) Lower byte. (3) For Each Elevation Cut, repeat E1-E23 (4) A halfword is defined to be 16 bits. All specified bit locations are referenced from 0 (the LSB) to 15 (the MSB). (5) Zero values are only to be used when the field is non-applicable. (6) Format defined as follows:

Angle Data Format

Angle Data Format (Degrees)

BIT # MEANING 15 180 deg 14 90 deg 13 45 deg 12 22.5 deg 11 11.25 deg 10 5.625 deg 9 2.8125 deg 8 1.40625 deg 7 0.70313 deg 6 0.35156 deg 5 0.17578 deg 4 0.08789 deg 3 (LSB) 0.043945 deg 2 X 1 X 0 X X = NOT APPLICABLE



SPG Build 10.0

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NOTE: A positive elevation angle is defined as being up from the horizontal plane, and a positive azimuth angle is defined as being clockwise from true north, when looking down at the radar. Elevation angles greater than 90 degrees will be interpreted as a negative angle and the actual elevation angle will be computed as the angle value minus 360 degrees. (7) Values shown are after applicable scaling and conversion is done. (8) Values are mutually exclusive. (9) Format defined as follows:

Azimuth and Elevation Rate Data BIT WEIGHT (1) (2) 0 X 1 X 2 X 3 0.010986328125 4 0.02197265625 5 0.0439453125 6 0.087890625 7 0.17578125 8 0.3515625 9 0.703125 10 1.40625 11 2.8125 12 5.625 13 11.25 14 22.5 15 Sign Bit (1 indicates negative) (3) Notes: 1. X indicates not applicable 2. Units are degrees per second. 3. Format is 2's complement binary scaled integer (i.e., Signed Integer *2) (10) See Appendix B for unit definitions and standard symbology. (11) Currently all operational VCP patterns are constant elevation types. (12) Clutter map groups are not currently used. The currently used value for this field is 1. (13) E value halfword locations are determined by EX = (12 + (X-1)) + ((Cut - 1) * Number_of_E_Values). Currently the Number_of_E_Values is 23. (14) These values are defined for TDWR/SPG VCP data but are currently not used or not applicable.



SPG Build 10.0

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Radial Data Header (Message Type 31): NAME DESCRIPTION FORMAT UNITS

(1) RANGE (2) ACCURACY/

PRECISION BYTE LOCATION (3)

Radar Identifier

ICAO Radar Identifier

String N/A (e.g., "TOKC") N/A 0 to 3

Collection Time

Radial data collection time in milliseconds past midnight GMT

Integer*4 msec 0 to 86,399,999 ± 2000/ 1

4 to 7

Modified Julian Date

Current Julian date - 2440586.5 (4)

Integer*2 d 1 to 65,535 1 8 and 9

Azimuth Number

Radial number within elevation scan

Integer*2 N/A 1 to 720 1 10 and 11

Azimuth Angle

Azimuth angle at which radial data was collected

Real*4 deg 0 to 359.956055

± 0.1 / NA

12 to 15

Compression Indicator

Indicates if message type 31 is compressed and what method of compression is used. The Data Header Block is not compressed.

Code*1 N/A 0 = uncompressed 1 = compressed using BZIP2 2 = compressed using zlib 3 = future use

N/A 16

Spare Spare and forces halfword alignment

N/A N/A N/A N/A 17

Radial Length

Uncompressed length of the radial in bytes including the Data Header block length

Integer*2 N/A 9352 to 14288 bytes

1 18 and 19

Azimuth Resolution Spacing

Azimuthal spacing between adjacent radials

Code*1 N/A 2 = 1.0 N/A 20

Radial Status

Radial Status (e.g. first, last)

Code*1 N/A 0 to 4 (6) N/A 21

Elevation Number

Elevation number within volume scan

Integer*1 N/A 1 to 23 1 22

Cut Sector Number

PRF Sectors Not Applicable

Integer*1 N/A 1 1 23

Elevation Angle

Elevation angle at which radial radar data was collected

Real*4 deg 0.0 to 60.0 ± 0.1 / NA

24 to 27

Radial Spot Blanking Status

Spot blanking status for current radial, elevation scan and volume scan

Code*1 N/A 0=none (7)

1=radial 2=elevation 4=volume

N/A 28



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NAME DESCRIPTION FORMAT UNITS (1)

RANGE (2) ACCURACY/ PRECISION

BYTE LOCATION (3)

Azimuth Indexing Mode

Azimuth indexing value (Set if azimuth angle is keyed to constant angles)(5)

Scaled Integer*1

N/A 0=no indexing 1 to 100 means indexing angle of 0.01 to 1.00

± 0.1 / 0.01

29

Data Block Count

Number of data blocks (N)

Integer*2 N/A 6 1 30 and 31

Data Block pointer

Pointer to Data Block for Volume Data Constant Type (8)

Integer*4 N/A 44 to 64 1 32 to 35

Data Block pointer

Pointer to Data Block for Elevation Data Constant Type (8)

Integer*4 N/A 84 or greater 1 36 to 39

Data Block pointer

Pointer to Data Block for Radial Data Constant Type (8)


Data Block pointer

Pointer to Data Block for Moment "REF" (9)


Data Block pointer

Pointer to Data Block for Moment "VEL" (9)


Data Block pointer

Pointer to Data Block for Moment "SW " (9)




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Data Block (Volume Data Constant Type): NAME DESCRIPTION FORMAT UNITS RANGE ACCURACY/


Data Block Type

Indicates Data Constant Type

String N/A "R" N/A 0

Data Name Volume Data Constant Block

String N/A "VOL" N/A 1 to 3

LRTUP (size of data block)

Size of data block in bytes

Integer*2 N/A 44

1 4 and 5

Version Number

Major Change (12) Integer*1 N/A 0 to 255

N/A 6

Version Number

Minor Change (13) Integer*1 N/A 0 to 255

N/A 7

Lat Latitude Real*4 deg 0.0 to 90.0

TBD/NA 8 to 11

Long Longitude Real*4 deg -180.0 to +180.0

TBD/NA 12 to 15

Site Height Height of site base above sea level

Integer*2 m 0 to 12000

± 1/1 16 and 17

Feedhorn Height

Same as Site Height Integer*2 m 0 to 12000

± 1/1 18 and 19

Calibration Constant (dBZ0)

Not Available Real*4 N/A 0.0 ± 1/ NA 20 to 23

Horizontal SHV Tx Power

Not Applicable Real*4 N/A 0.0 NA 24 to 27

Vertical SHV Tx Power


System Differential Reflectivity


Initial System Differential Phase

Not Applicable Real*4 N/A 0.0 ± 1.0 /NA 36 to 39

Volume Coverage Pattern Number

Identifies Volume Coverage Pattern being used

Integer*2 N/A 80 or 90 1 40 and 41

Processing Status

Not Applicable Integer*2 N/A 0 N/A 42 and 43



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Data Block (Elevation Data Constant Type): NAME DESCRIPTION FORMAT UNITS RANGE ACCURACY/


Data Block Type

Indicates Data Constant Type


Data Name Elevation Data Constant Block

String N/A "ELV" N/A 1 to 3



Integer*2 N/A 12

1 4 and 5

ATMOS Atmospheric Attenuation Factor

Scaled SInteger*2

dB/km -0.02 to -0.002

± 0.004/ 0.001

6 and 7

Calibration Constant (dBZ0)

Not Available Real*4 N/A 0.0 N/A 8 to 11

Data Block (Radial Data Constant Type): NAME DESCRIPTION FORMAT UNITS RANGE ACCURACY/


Data Block Type Indicates Data Constant Type


Data Name Radial Data Constant Block

String N/A "RAD" N/A 1 to 3



Integer*2 N/A 28 1 4 and 5

Unambiguous Range (21)

Unambiguous range, Interval Size

Scaled Integer*2

km 75-600 ± 0.1/ 0.1

6 and 7

Noise Level Not Available Real*4 N/A 0.0 N/A 8 to 11 Noise Level Not Applicable Real*4 N/A 0.0 N/A 12 to 15 Nyquist Velocity Not Available Integer*2 N/A 0

N/A 16 and 17

Radial Flags Not Applicable Integer*2 N/A 0 N/A 18 and 19 Calibration Constant(dBZ0)

Not Available Real*4 N/A 0.0 N/A 20 to 23

Calibration Constant(dBZ0)

Not Applicable Real*4 N/A 0.0 N/A 24 to 27



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Data Moment Characteristics and Conversion for Data Names:

Data Name

Data Moment Description

Data Word Size (bits)

Data Size (bits) (14)

Format Offset (10)

Scale (10)

Data Range As coded

Data Range after conversion

Units Accuracy/ Precision (17)

Range (km)

LDM (11)

"REF " Reflectivity (Z)

8 8 Integer*1 66.0 2.0 2 to 255 (16) -32.0 to +94.5

dBZ ± 1.0/ 0.50

90/417 (19)

300/ 1390

"VEL " Velocity (V)

8 8 Integer*1 129.0 2.0 or 1.0

2 to 255 (16) -63.5 to +63.0 or -80.0 to +80.0

m/s ± 1.0/0.50 or ± 1.0/1.00

90 300

"SW " Spectrum Width (σ)

8 8 Integer*1 129.0 2.0 129 to149 (16)

0.0 to +10.0 m/s ± 1.0/ 0.50

90 300

Data Block (Descriptor of Generic Data Moment Type) NAME DESCRIPTION FORMAT UNITS RANGE ACCURACY/


Data Block Type

Indicates Data Moment Type String N/A "D" 1 0

Data Moment Name

Name of data moment String N/A "VEL", "REF", "SW"

1 1 to 3

Reserved (18) Reserved (18) Integer*4 N/A Set to 0 1 4 to 7 Number of Data Moment Gates

Number of data moment gates for current radial (NG)

Integer*2 N/A 0 to 1840 1 8 and 9

Data Moment Range

Range to center of first range gate Scaled Integer*2

km 0.000 to 32.768

± 0.05/ 0.001

10 and 11

Data Moment Range Sample Interval

Size of data moment sample interval Scaled Integer*2

km 0.15 or 0.3 ± 0.05/ 0.001

12 and 13

TOVER Threshold parameter which specifies the minimum difference in echo power between two resolution gates for them not to be labeled "overlayed"

Scaled Integer*2

dB 5.0 ± 0.1/ 0.1

14 and 15

SNR Threshold SNR threshold for valid data Scaled SInteger*2

dB -12.0 to +20.0

±0.1/0.125 16 and 17

Control Flags Indicates special control features Code*1 N/A 0 = none

1 18

Data Word Size Number of bits (DWS) used for storing data for each Data Moment gate

Integer*1 N/A 8 or 16 1 19

Scale Scale value used to convert Data Moments from integer to floating point data (10)

Real*4 N/A Greater than 0.0 to 65535.0

1 20 to 23

Offset Offset value used to convert Data Moments from integer to floating point data (10)

Real*4 N/A 2.0 to 65535.0

1 24 to 27



SPG Build 10.0

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The first three blocks of every radial are the Volume Constant Block, followed by the Elevation Constant Block, followed by the Radial Constant Block. Following these blocks are the following blocks in the order presented. Some of data blocks may not be available based on the VCP wave form for the elevation cut. Data Block # 3 (Reflectivity Data) NAME DESCRIPTION BYTE LOC Data Block Type Character (“D”) 0 Data Moment Name Characters (“REF”) 1 to 3 Reserved (18) Reserved (18) 4 to 7 Number of Data Moment Gates Number of range samples for current radial 8 and 9 Data Moment Range Range to center of first range gate (m) 10 and 11 Data Moment Range Sample Interval Size of range sample interval (m) 12 and 13 (19) TOVER Range folding threshold determination 14 and 15 “REF” SNR Threshold Signal to Noise Threshold For Reflectivity 16 and 17 Control Flags Not Used (set to 0) 18 Data Word Size Number of bits used for each data moment sample 19 Scale Scale to convert from integer to floating point data (10) 20 and 21 Offset Offset to convert from integer to floating point data (10) 22 and 23 Moment Data (“REF”) Variable length array of moment data 24 - Data Block # 4 (Velocity Data) NAME DESCRIPTION BYTE LOC Data Block Type Character (“D”) 0 Data Moment Name Characters (“VEL”) 1 to 3 Reserved (18) Reserved (18) 4 to 7 Number of Data Moment Gates Number of range samples for current radial 8 and 9 Data Moment Range Range to center of first range gate (m) 10 and 11 Data Moment Range Sample Interval Size of range sample interval (m) 12 and 13 (20) TOVER Range folding threshold determination 14 and 15 “VEL” SNR Threshold Signal To Noise for Velocity 16 and 17 Control Flags Not Used (set to 0) 18 Data Word Size Number of bits used for each data moment sample 19 Scale Scale to convert from integer to floating point data (10) 20 and 21 Offset Offset to convert from integer to floating point data (10) 22 and 23 Moment Data (“VEL”) Variable length array of moment data 24 - Data Block # 6 (Spectrum Width Data) NAME DESCRIPTION BYTE LOC Data Block Type Character (“D”) 0 Data Moment Name Characters (“SW”) 1 to 3 Reserved (18) Reserved (18) 4 to 7 Number of Data Moment Gates Number of range samples for current radial 8 and 9 Data Moment Range Range to center of first range gate (m) 10 and 11 Data Moment Range Sample Interval Size of range sample interval (m) 12 and 13 (20) TOVER Range folding threshold determination 14 and 15 “SW” SNR Threshold Signal To Noise threshold for Spectrum Width 16 and 17 Control Flags Not Used (set to 0) 18 Data Word Size Number of bits used for each data moment sample 19 Scale Scale to convert from integer to floating point data (10) 20 and 21 Offset Offset to convert from integer to floating point data (10) 22 and 23 Moment Data (“SW”) Variable length array of moment data 24 -



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(1) See Appendix B for unit definitions and standard symbology. (2) This field represents the range of the item after any applicable scaling and conversion is done. (3) Byte location is relative to beginning of this message. (4) 1 January 1970 00.00 GMT = 1 Modified Julian Date. (5) Azimuthal spacing of radials is the commanded value not necessarily the actual spacing. (6) Format Defined as follows (Radial status definition):

Radial Status Data Format Radial Status Indicator (Hex)

Setting (Hex)

Start of new Elevation 00 Intermediate Radial Data 01 End of Elevation 02 Beginning of Volume Scan 03 End of Volume Scan 04 (7) Equals 0 when spot blanking disabled; equals 4 when spot blanking enabled and no spot blanking radials in current elevation cut; equals 6 when there are no spot blanked radials in current elevation cut and current radial not spot blanked; equals 7 when current radial is spot blanked. (8) Pointer is offset relative to beginning of Data Header Block. Note the Data Header Block for data blocks "VOL", "ELV", and "RAD" must always be present but the pointers are not order or location dependent. (9) Pointer is offset relative to beginning of Data Header Block but if the pointer value is 0, there is no Data Moment Block referenced. Normally, if the Data Moment is missing, this pointer would not be present and the Data Block Count reduced. However, it is optional to set pointers to zero or simply delete the pointer to the missing Data Moment Block. (10) A non-zero Scale value indicates unsigned integer data that can be converted to floating point data using the Scale and Offset fields, i.e., F = (N - OFFSET) / SCALE where N is the integer data value and F is the resulting floating point value. A scale value of 0 indicates floating point moment data for each range gate. (11) LDM is the amount of space in bytes required for a data moment array and equals ((NG * DWS) / 8) where NG is the number of gates at the gate spacing resolution specified and DWS is the number of bits stored for each gate (DWS is always a multiple of 8). (12) Major version number. A larger major version number indicates a structural change has occurred within the ICD description. The current version is 0. (13) Minor version number. A larger minor version number indicates that one or more data moment parameters have been added but the major structure is intact. The current version is 0. (14) Data Size is the number of bits for the specified data moment used to offset and scale the data for recording into the Data Word Size (DWS). As long as the Offset and Scaling parameters are applied correctly to the recorded data for conversion back to engineering units, no knowledge of the Data Size is needed. (15) The Scale and Offset values shown in Data Moment Characteristics and Conversion for Data Names Table are typical values for the Moments shown. The conversion of the recorded integer values to meteorological values should always use the Scale and Offset values found in the Data Moment Block for each Data Moment since they could change from radial to radial in future implementations. (16) For all Reflectivity, Velocity, and Spectrum Width integer values N = 0 indicates received signal is below threshold and N = 1 indicates range folded data. Actual data range begins at N = 2. (17) The precision can be calculated exactly as 1.0/Scale but is shown here with only a selected number of significant digits.



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(18) "Reserved" means the field has a specific future use but not implemented at this time and must be set to zero. The field is not a "Spare" available for arbitrary future use. (19) “REF” data has two sample interval sizes, 150 m and 300 m. For the long range surveillance scan (wave form type Contiguous Surveillance), the range sample interval is 300 m. For all other wave form types, the sample interval is 150 m. (20) “VEL” and “SW” have range sample interval of 150 m. (21) Unambiguous range can change from radial to radial.

2620075 icd for spg to archive ii user

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